Double-base propellant containing poly (carboranyl lower alkyl acrylate)

ABSTRACT

A double-base rocket propellant comprising (1) nitrocellulose, (2) poly (carborane lower alkyl acrylate) and (3) a nitrato compound or mixtures of nitrato compounds and which may additionally contain plasticizers, stabilizers, burning rate modifiers, fuels and oxidizers.

United States Patent Elrick 1 1 Mar. 25, 1975 [54] DOUBLE-BASE PROPELLANT ggggDSg (gversohl it al... 149/98 X NT p LY ARBORANYL ,41 erry e! a 149/22 fig i sg gi 3,444,013 5/1969 Green Ct a1. 1 149/22 3,445,304 5/1969 Cahill et a1. 149/22 X [75] Inventor; Donald E, Elrick, Rawlings, Md, 3,489,623 1/1970 Griffith et al..... 149/38 X 3,535,172 10/1970 Bieber et a1. 149/22 X 1 Asslgneer The Unlted States of Amerlca as 3,791,893 2 1974 1-1111 149/19 2 represented y the Secretary of the 3,811,966 5/1974 Hill et d1 149/19 2 Navy, Washington, DC.

[22] Filed: June 28, 1971 Primary ExaminerBenjamin R. Padgett Assistant ExaminerE. A. Miller [21] Appi' (L076 Attorney, Agent, or FirmR. S. Sciascia; .1. A. Cooke [521 11.5. CI l49/l9.2, 149/19.8, 149/22,

149/38, 149/20, 149/92, 149/93, [57] ABSTRACT {5 H Int Cl L 82 A double-base rocket propellant comprising (1) nitrolsgl Fie'ld 100 92 cellulose, (2) poly (carborane lower alkyl acrylate) 49/93 75 1 and (3) a nitrato compound or mixtures of nitrato compounds and which may additionally contain plasticizers, stabilizers, burning rate modifiers, fuels and ox- [56] References Cited ldlzers' 3,254,115 5/1966 Cohen et a1. 149/22 X DOUBLE-BASE PROPELLANT CONTAINING POLY (CARBORANYL LOWER ALKYL ACRYLATE) BACKGROUND OF THE INVENTION This invention generally relates to double-base rocket propellants and more particularly to doublebase rocket propellants which contain poly (carborane lower alkyl acrylate).

Double-base rocket propellants, which usually contain nitrocellulose and a nitrato compound, are well known in the prior art. In addition, these propellants can also contain various additives such as plasticizers, stabilizers, fuels, oxidizers and burning rate modifiers. With respect to burning rate modifiers, it is desirable to use materials which will maximize the burning rate but which will not volatilize when exposed to elevated temperatures. Research has constantly sought materials which significantly increase the burning rate of doublebase propellants, which do not volatilize when exposed to elevatated temperatures and which do not adversely effect the other properties of the propellant.

SUMMARY OF THE INVENTION Accordingly, one object of this invention is to provide a double-base propellant.

Another object of this invention is to provide a double-base propellant which has a relatively good burning rate.

A further object of this invention is to provide a double-base propellant which has a burning rate modifier that is relatively non-volatile even when exposed to relatively high temperatures.

A still further object of this invention is to provide a method for increasing the burning rate of double-base propellants.

These and other objects of this invention are accomplished by providing double-base propellants comprising (1) nitrocellulose, (2) poly (carborane lower alkyl acrylate) as a burning rate modifier and (3) a nitrato compound or mixtures of nitrato compounds and which may additionally contain plasticizers, stabilizers, other burning rate modifiers, fuels and oxidizers.

DESCRIPTION OF THE PREFERRED EMBODIMENT The double-base propellants of this invention contain nitrocellulose which preferably constitutes -35 weight percent of the propellant. Although the nitrogen content of the nitrocellulose is not a critical factor, it is desirable to use nitrocellulose which has a nitrogen content of between about 11.0 and 13.2%.

The poly (carborane lower alkyl acrylate), which is a burning rate modifier, preferably constitutes between 3 and weight percent of the propellant. The term lower alkyl is meant to cover alkyl of l to 6 carbon atoms. Although the exact molecular weight of this polymer is not a critical feature of this invention, it is desirable to have lower molecular weight products such as that which was prepared in Example I, hereinafter presented. It is, however, not recommended that very high molecular weight polymers be used because the higher the molecular weight the greater the crosslinking of the polymer and therefore the more difficult it is to form a homogeneous propellant. However, the lower the molecular weight the more likely the polymer is to volatilize when exposed to elevated temperatures.

Thus, the preferred materials are those with a specific viscosity of about 0.05-0.20 as about a 1.04g sample in ml of acetone at 50C.

As with all other double-base propellants, at least one other nitrato compound or mixture of nitrato compounds is required. Examples of nitrato compounds are nitroglycerin, diethyleneglycol dinitrate, 1,2,4- butanetriol trinitrate, l,l,l-trimethylol ethane trinitrate, pentaerythitol trinitrate, dinitrolycerin and the like with nitroglycerin being the most widely used and most preferred. The nitrato compound or mixture of nitrato compounds preferably constitutes 30-55 weight percent of the instant propellant.

Besides the above listed ingredients, the propellant may also include a number of other ingredients in the propellant composition. Thus stabilizers such as- 2- nitrodiphenylamine (NDPA), ethyl centralite, resorcinol, N-methyl paranitroaniline and the like or mixtures of stabilizers may be used. The stabilizer preferably constitutes from 0.5-3.0 weight percent of the propellant composition.

Similarly, plasticizers may be added to the instant propellant composition. Triacetin is a particularly preferred plasticizer but any of the other art recognized plasticizers, such as for example, isophorone, or mixture of plasticizers will work. The plasticizer preferably constitutes 3-8 weight percent of the propellant.

Additionally, metal fuels may be added to the propel-' lant composition. Typical of the metal fuels that may be added are the free metals of aluminum, beryllium, zirconium, aluminum/magnesium alloy and the like or mixtures of these various metals. All of these tend to increase the propellant density and improve specific impulse. When used in the propellant, the metal fuel preferably constitutes 4-20 weight percent of the composition.

Oxidants may also be added to the propellant composition. Generally when oxidants are added, the propellant is usually referred to as a composite-modified double-base propellant. Typical oxidant additives that can be used with the propellant of the instant invention in-' clude all the art recognized oxidant additives such as, for example, perchlorates of ammonium, potassium, lithium and nitronium as well as nitrates such as ammonium nitrate, potassium nitrate, lithium nitrate, hydrazine nitrate and nitramines such as I-IMX, RDX, pentaerythritol tetranitrate, trinitrotoluene, nitroguanidi'ne and the like. This constituent constitutes 0-40 weight percent of the propellant.

Furthermore, the art recognized burning rate modifiers such as lead salts and carbon black may also be included in the propellant composition as a partial replacement for up to about half of the poly (carborane lower alkyl acrylate) that is to be used in the propellant composition.

The general nature of the invention having been set forth, the following examples are presented as specific illustrations thereof. It will be understood that the invention is not limited to these specific examples but is suceptible to various modifications that will be recognized by one of ordinary skill in the art.

EXAMPLE I Poly (carborane methyl acrylate) A solution of carborane methyl acrylate (OMA) in pentane was distilled from a flask equipped with a Vigreaux column to obtain 16.8g of (MA, b.p. 134C at 3 mm, n 1.5430. To a six ounce crown-cap bottle was added 16.72g of OMA, 0.20g t-butyl perbenzoate and 152g methyl ethyl ketone. The contents of the bottle were sparged with nitrogen and the bottle was then capped and heated for four days at 60C. The methyl ethyl ketone was removed by air sparging and by heating at 30C at a pressure of about 4 mm Hg. Chloroform (100 ml) was added to dissolve the semi-solid that had formed. The chloroform solution was washed with a solution containing 3 ml of 0.5N sodium hydroxide in 100g of water and then with water using a Mag-Mix stirrer to provide agitation. The chloroform solution was dried over magnesium sulfate and placed in a 200 ml flask. Chloroform was removed from the flask by air sparging and then by heating at 30C at reduced pressure while rotating the flask on a Roto-Vac to leave a semi-solid which had a specific viscosity of 0.11 at a concentration of l.04g/100 ml in acetone.

EXAMPLE [I A typical propellant formulation was prepared with the above polymer and its composition was as follows:

71 by weight Nitrocellulose (I267: N content) 235 poly OMA prepared above 6.0

Nitroglycerine 8.0

Aluminum powder l0.0

Ammonium Perchlorate 50.0

Resorcinol 1.5

Nitrodiphenylamine I .0

50 grams of a coating powder of the above composition was combined in a small casting with the appropriate amount of a casting solvent which contained '72 by weight Nitroglycerin 75 Triacetin 24 Nitrodiphenylamine l The casting was cured for two day at 25C and seven days at 60C.

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described herein.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

l. A solid double-base rocket propellant comprising nitrocellulose, poly (carborane lower alkyl acrylate) and a nitrato constituent selected from the group consisting of a nitrato compound and mixtures of nitrato compounds.

2. The propellant composition of claim 1 wherein nitrocellulose constitutes 10-35 weight percent, poly (carborane lower alkyl acrylate) constitutes 3-15 weight percent and the nitrato constituent comprises 30-55 weight percent of the composition.

3. The propellent composition of claim 1 which additionally contains a material selected from the group consisting of plasticizers, stabilizers, burning rate modifiers, fuels, oxidizers and mixtures thereof.

4. The propellant compositon of claim 2 wherein said nitrato constituent is selected from the group consisting of nitroglycerin, diethyleneglycol dinitrate, 1,2,4- butanetriol trinitrate, l,l,l-trimethylol ethane trinitrate, pentaerythitol trinitrate, dinitroglycerin and mixtures thereof.

5. The propellant composition of claim 3 wherein said nitrato constituent is selected from the group consisting of nitroglycerin, diethyleneglycol dinitrate, 1,2,4-butanetriol trinitrate, 1,1,I-trimethylol ethane trinitrate, pentaerythitol trinitrate, dinitroglycerin and mixtures thereof.

6. The propellant composition of claim 5 wherein said plasticizer is selected from the group consisting of triacetin, isophorone and mixtures thereof, said stabilizer is selected from the group consisting of 2- nitrodiphenylamine, ethyl centralite, resorcinol, N- methyl paranitroaniline and mixtures thereof, such burning rate modifier is selected from the group consisting of lead salts, carbon black and mixtures thereof, said fuel is selected from the group consisting of aluminum, beryllium, zirconium, aluminum/magnesium alloy and mixtures thereof and said oxidizer is selected from the group consisting of ammonium perchlorate, potassium perchlorate, lithium perchlorate, nitronium perchlorate, ammonium nitrate, potassium nitrate, lithium nitrate, hydrazine nitrate, HMX, RDX, pentaerythritol tetranitrate, trinitrotoluene, nitroguanidine and mixtures thereof.

7. The propellant composition of claim 6 wherein said plasticizer constitutes about 38 weight percent, said stabilizier constitutes about O.5-3.0 weight percent, said burning rate modifier constitutes not more than a weight percent equal to that pf poly (carborane lower alkyl acrylate), said fuel constitutes 420 weight percent and said oxidizer constitutes 0-40 weight percent of said propellant composition.

8. The propellant composition of claim 2 wherein the specific viscosity of the poly (carborane lower alkyl acrylate) is about 005-020 when measured as about a l.04g sample in ml of acetone at 50C.

9. The propellant composition of claim 6 wherein the specific viscosity of the poly (carborane lower alkyl acrylate) is about 0.05-0.20 when measured as about a l.04g sample in 100 ml of acetone at 50C.

10. A method of modifying the burning rate of a double-base propellant comprising adding poly (carborane lower alkyl acrylate) to said propellant. 

1. A SOLID DOUBLE-BASE ROCKET PROPELLANT COMPRISING NITROCELLULOSE, POLY(CARBORANE LOWER ALKYL ACRYLATE) AND A NITRATO CONSTITUENT SELECTED FROM THE GROUP CONSISTING OF A NITRATO COMPOUND AND MIXTURES OF NITRATO COMPOUNDS.
 2. The propellant composition of claim 1 wherein nitrocellulose constitutes 10-35 weight percent, poly (carborane lower alkyl acrylate) constitutes 3-15 weight percent and the nitrato constituent comprises 30-55 weight percent of the composition.
 3. The propellent composition of claim 1 which additionally contains a material selected from the group consisting of plasticizers, stabilizers, burning rate modifiers, fuels, oxidizers and mixtures thereof.
 4. The propellant compositon of claim 2 wherein said nitrato constituent is selected from the group consisting of nitroglycerin, diethyleneglycol dinitrate, 1,2,4-butanetriol trinitrate, 1,1,1-trimethylol ethane trinitrate, pentaerythitol trinitrate, dinitroglycerin and mixtures thereof.
 5. The propellant composition of claim 3 wherein said nitrato constituent is selected from the group consisting of nitroglycerin, diethyleneglycol dinitrate, 1,2,4-butanetriol trinitrate, 1,1,1-trimethylol ethane trinitrate, pentaerythitol trinitrate, dinitroglycerin and mixtures thereof.
 6. The propellant composition of claim 5 wherein said plasticizer is selected from the group consisting of triacetin, isophorone and mixtures thereof, said stabilizer is selected from the group consisting of 2-nitrodiphenylamine, ethyl centralite, resorcinol, N-methyl paranitroaniline and mixtures thereof, such burning rate modifier is selected from the group consisting of lead salts, carbon black and mixtures thereof, said fuel is selected from the group consisting of aluminum, beryllium, zirconium, aluminum/magnesium alloy and mixtures thereof and said oxidizer is selected from the group consisting of ammonium perchlorate, potassium perchlorate, lithium perchlorate, nitronium pErchlorate, ammonium nitrate, potassium nitrate, lithium nitrate, hydrazine nitrate, HMX, RDX, pentaerythritol tetranitrate, trinitrotoluene, nitroguanidine and mixtures thereof.
 7. The propellant composition of claim 6 wherein said plasticizer constitutes about 3-8 weight percent, said stabilizier constitutes about 0.5-3.0 weight percent, said burning rate modifier constitutes not more than a weight percent equal to that pf poly (carborane lower alkyl acrylate), said fuel constitutes 4-20 weight percent and said oxidizer constitutes 0-40 weight percent of said propellant composition.
 8. The propellant composition of claim 2 wherein the specific viscosity of the poly (carborane lower alkyl acrylate) is about 0.05-0.20 when measured as about a 1.04g sample in 100 ml of acetone at 50*C.
 9. The propellant composition of claim 6 wherein the specific viscosity of the poly (carborane lower alkyl acrylate) is about 0.05-0.20 when measured as about a 1.04g sample in 100 ml of acetone at 50*C.
 10. A method of modifying the burning rate of a double-base propellant comprising adding poly (carborane lower alkyl acrylate) to said propellant. 